FATHER ANGELO SECCHI BY WILLIAM F. RIGGE REPRINTED FROM POPULAR ASTRONOMY, VOL. XXVI, NO. 259, NOVEMBER, 1919 FATHER ANGELO SECCHJ. WILLIAM F. RIGGE. A century ago, on June 29,1818, there was born at Reggio in AEmilia, Italy, a child that was destined to become one of the greatest astrono­ mers of his age. He was to open up new avenues of research and to be the founder of important branches of science. In his person religion and science were happily blended. Both as a Jesuit and as an astronomer, his character has ever been undimmed and unimpeached. It is a pleasure, then, and a privilege to write his eulogy, and to narrate his achievements. Little or nothing is known of Father Secchi’s childhood. That it was passed in innocence and integrity is shown by the fact that on November 3,1833, only four months beyond the minimum age of fifteen years F ather A ngelo Secchi that its constitutions permitted he entered the Jesuit order. He passed successfully through his three years of probation, two of literature, three of philo­ sophy and science, and four of theology, and was raised to the dignity of the priesthood at the usual time. He early disclosed his predilection and his talents for the sciences in which he was to achieve his renown. He was accordingly appointed to teach mathematics at Rome in the College of Nobles, and then at the Roman College. Later he taught physics at Loretto, and after this was an assistant to Father DeVico in the observatory of the Roman College, the first that the Jesuits were able to establish since the restoration of their order in 1814. Great as was the reputation of the master, the pupil was soon to eclipse him in the same science and in the same place. The revolution of 1848 seemed to nip all these fair prospects in the bud. The Jesuits had to flee from Rome. DeVico went to France, and 2 Father Angelo Secchi then to Georgetown College, in Washington, D. C., whither Secchi soon followed him. Here the latter taught physics for a year and made original discoveries in electricity. When the revolution subsided in the following year, Father Secchi was recalled to Rome, and, as DeVico had died in the previous November, he was appointed director of the Roman College Observa­ tory. At the early age of thirty-one years Angelo Secchi now entered upon the career for which his talents and his industry so admirably qualified him, and quickly became one of the foremost scientists of his age. His first care was to build a proper observatory and to furnish it with suitable instruments. With means liberally supplied by Pius IX and the Society of Jesus, he in 1853 transferred the existing observa­ tory to the place his predecessors had selected, and built it upon the east and south walls of the college and upon the principal pilasters of the church of St. Ignatius. His main instrument was a nine-inch equatorial telescope. While this would be considered nowadays quite an ordinary size for the student’s observatory of a university, and no match for our modern giants, still in its day it was one of the great telescopes of the world. But it was directed by a genius of the first order, who well knew how to use it, and who did use it with an energy that never felt fatigue. To look at his published reports and articles and books, one would imagine he used it day and night continuously without ever stopping to rest. No class of heavenly bodies escaped his scrutiny, the sun, the moon, the individual planets, comets, and thousands of stars, were observed with an assiduity and an accuracy that seemed to make each one the pet object of his research. Father Secchi’s work on the sun and the stars will be remembered as long as the science of astronomy will endure, for he was one of the great pioneers, one of the great founders of a new branch of astronomy. He was one of the very first to apply the newly invented spectroscope to the heavenly bodies, and to see its possibilities and the enormous harvest of knowledge it would yield. He was also quick to see the soul of the new instrument and to design various types of spectro­ scopes. One has but to open a recent and authoritative treatise on the subject, such as Schemer’s Astronomical Spectroscopy by E. B. Frost, now and for some time director of the Yerkes Observatory, in order to see how Secchi’s ideas are still embodied in our present day instruments. One of the forms with which he did a great part of his work on stellar spectra, and which is “described arid illustrated in all text books on spectrum analysis” (Frost, page 29) is called the objective- prism spectroscope. Here the prism is a large one and is placed outside and in front of the objective of the telescope, thus utilizing to advantage the full focal length of the tube. William F. Rigge 3 In the second form “devised by Secchi” (Frost p. 30) the prism or system of prisms is placed inside the telescope tube and intercepts the rays of light just before they come to a focus. And in a third one, figured in all treatises and called Secchi’s star spectroscope, the whole spectroscope with its collimator, prism system and view telescope, is put outside of the eye end of the large telescope. And lastly, he was the first to “make the curious and interesting” combination (Frost p. 109) of this third form of the spectroscope with the first. Not only did Secchi design spectroscopes, but he used them with an intelligence and an assiduity that have justly immortalized him. The sun claimed the greatest share of his attention, on account, not only of the more congenial time of its appearance but also of its abundance of light, which permits of such minute analysis of its features. Father Secchi studied the sun most thoroughly, and by applying to it his telescope, spectroscope and photographic camera, by examining in every conceivable way its photosphere, chromosphere, spots, faculae, prominences and corona, he was in a position to formulate a theory of its constitution, of the nature, formation and dissolution of its spots and prominences, and of its entire body. This theory has received the highest commendation from all the greatest astronomers during and since his time. Thus the late Simon Newcomb, acclaimed to have been the greatest mathematical astronomer of his day, devotes a considera­ ble space in his text book of P opular A stronomy to what he calls “Secchi’s first theory” and “Secchi’s later theory” of sunspots. Langley, at his death director of the observatory of the Smithsonian Institution in Washington, gives a number of Secchi’s illustrations in his New Astronomy. And “Secchi’s typical sunspot” as well as other figures and theories still appear in every popular and technical treatise on the sun, such as, to mention only one, Young’s The Sun and Abbot’s revision of the book. G. E. Hale, first director of the Yerkes Observa­ tory, and now of that of Mount Wilson, one of the greatest living authorities on the sun, has the deepest respect for the name of Angelo Secchi, as his numerous publications abundantly show. It was no doubt at his initiative that at the Fourth Conference of the International Union for Cooperation in Solar Research, held at Mount Wilson, August 29-September 3, 1910, the resolution was adopted “that the fund raised in Italy as a memorial to Father Secchi be devoted to the construction of a tower telescope” (P opular A stronomy XVIII, 500). Two of Father Secchi’s brothers in religion were present at this con­ ference, Fr. A. Cortie of Stonyhurst College Observatory in England, held to be the best informed on the connection between sunspots and terrestrial magnetism, and Fr. R. Cirera, of the Ebro Observatory in Spain, whose specialty is the study of the connection between changes on the sun and changes in our weather. 4 Father Angelo Secchi Along with De la Rue, Secchi deserves the distinction of having been the first to photograph the sun’s corona during a total eclipse. This happened July 18, 1860, in Spain. As nothing at all was known at the time of the character of the plate to be used, its degree of sensi­ tiveness, the length of the exposure, and of many other details, “a shot had to be fired in the dark” as Miss Clerke expresses it in her History of Astronomy during the Nineteenth Century (Second edition, page 211). It had not even been proved at the time that the prominences and the corona really belonged to the sun instead of to the eclipsing moon or to our own atmosphere. The photographs taken at this eclipse established this point to a certainty, since the two observers were about 250 miles apart, and their photographs showed not only identical details, but also the moon’s motion over them in the interval. Father Secchi embodied his discoveries on the sun in a work which will always be considered a classic in astronomical literature. It was entitled Le Soleil and was written in French and printed in Paris in 1870. It is mentioned in every treatise on the sun that has appeared since, and its illustrations are largely drawn upon even at present. A second edition appeared five years later and was soon after translated into German, Spanish, Italian and other languages.